Ronald Guida wrote:
> How do I create C-libraries that I can load into GHCi? I am trying to
> do some basic FFI, and it's not working.
So, after more searching on the internet and some RTFM, I think I
found my answer, and it seems to work, but I don't know if it's the
right answer to generalize from.
1. I can leave "test_foo.lhs" and "foo.cpp" as-is.
2. I need to change "foo.h" to the following:
------------------
// foo.h
#if BUILD_DLL
#define DECLSPEC __declspec(dllexport)
#else
#define DECLSPEC __declspec(dllimport)
#endif
extern "C"
{
DECLSPEC __stdcall int foo(int x);
}
------------------
3. I need to create a DEF file and list the functions to be exported
in a DLL.
------------------
foo.def
------------------
LIBRARY foo
DESCRIPTION "Foo Library"
EXPORTS
foo
------------------
Note: The library name on the first line must match the dll name.
"LIBRARY foo" corresponds to "foo.dll"
4. The build process is as follows.
(1) gcc -DBUILD_DLL -c foo.cpp
(2) gcc -shared -o foo.dll foo.o foo.def \
-Wl,--enable-stdcall-fixup,--out-implib,libfoo.a
5. At this point, I'll have "foo.dll" and "libfoo.a". I can load my
"foo" library, as a DLL, into GHCi with the command:
$ ghci -lfoo
In reality, I would use:
$ ghci test_foo.lhs -lfoo
6. Once I'm satisfied and ready to compile:
ghc --make test_foo.lhs -L. -lfoo
Notes:
(1) "-L." directs GHC to look in the current directory for
libraries. GHCi seems to look there by default.
(2) The resulting "test_foo.exe" will dynamicly load "foo.dll".
7. If I want a staticly linked executable instead:
ar rcs libfoo_static.a foo.o
ghc --make test_foo.lhs -L. -lfoo_static
8. Finally, I can put the build steps into a makefile.
------------------
# Makefile for foo
test_foo.exe : test_foo.lhs libfoo.a foo.dll
ghc --make test_foo.lhs -L. -lfoo
test_foo_static.exe : test_foo.lhs libfoo_static.a
ghc --make test_foo.lhs -L. -lfoo_static -o test_foo_static.exe
libfoo.a : foo.dll
foo.dll : foo.o foo.def
gcc -shared -o foo.dll foo.o foo.def \
-Wl,--enable-stdcall-fixup,--out-implib,libfoo.a
libfoo_static.a : foo.o
ar rcs libfoo_static.a foo.o
foo.o : foo.cpp foo.h
gcc -DBUILD_DLL -c foo.cpp
.PHONY: clean
clean:
rm -f *.[oa]
rm -f *.dll
rm -f *.hi
rm -f *.exe
------------------
-- Ron
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